Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and a rotor including one or more rotor blades. The rotor blades capture kinetic energy from wind using known foil principles and transmit the kinetic energy through rotational energy to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
During operation of a wind turbine, various components of the wind turbine are subjected to various loads due to the aerodynamic wind loads acting on the blade. In particular, the main shaft coupling the rotor blades and the generator may be subjected to various loads due to the wind loading acting on the rotor blades and resulting reaction loads being transmitted to the shaft. Such loading may include, for example, axial loads and moment loads, such as bending moment loads and torsional (twisting) moment loads. Deflection of the shaft due to these loads may thus frequently occur during operation of the wind turbine. When the loads are significantly high, substantial damage may occur to the rotor shaft, pillow blocks, bedplate and/or various other component of the wind turbine. Thus, the moment loads induced on the shaft due to such loading are particularly critical variables, and in many cases should desirably be monitored and, if necessary, controlled during operation of the wind turbine.
However, currently known systems and methods for monitoring such loads can be difficult to implement and service due to, for example, physical constraints leading to load measurement inaccuracies. For example, proximity probes may be mounted to monitor displacement of a flange on the shaft. However, such probes must be mounted in relatively stable locations, which are typically in small, inaccessible areas, thus making it difficult to install and maintain the probes. Further, such probes require expensive, durable mounting hardware. Still further, the data provided by these probes provides only indirect measurements of the loads to which the shaft is subjected. These various disadvantages can result in inaccuracy and decreased reliability. Further, many monitoring systems are not capable of providing torsional measurements of the drivetrain system. While applications of strain gauges attached to the main shaft have been described and are practiced for measurement of both bending and torsional loads, a variety of challenges (manufacturing, service, data communication from rotating element) with these approaches lead to inaccuracy and poor reliability.
Thus, an improved system and method for monitoring loads in a wind turbine is desired. For example, a system and method that provide more accurate and reliable measurements of shaft loading would be advantageous.